UNIVERSITY PARK, Pa. -- The Y chromosomes of cattle have more genes and are more active than the Y chromosomes of other primates, according to researchers.
This discovery may help biologists better understand how cattle and other mammals evolved, as well as help animal breeders and farmers better maintain and enhance fertility in the cattle industry, said Wansheng Liu, associate professor of animal genomics, Penn State.
"Low fertility is a big problem for the dairy and beef industry," Liu said. "In the past 60 years, we paid more attention to milk, or beef production as a sign of herd success, but, even as milk production goes up, the animal's fertility goes down, which means it's time to pay more attention to male fertility now."
The researchers identified 1,274 genes in the male specific region of the bovine Y chromosome, compared to the 31 to 78 genes associated in the Y chromosomes of various primates. They also said the genes in the bovine Y chromosome were much more transcriptionally active compared to other mammals. Transcription is the first step of gene expression when DNA is copied. In this process, the cell produces messenger RNA that copies the genetic information from the cell nucleus to serve as a template for protein synthesis.
In addition to the 1,274 genes that take part in coding proteins, they also identified 375 novel noncoding gene families on the bovine Y chromosome, which are predominantly expressed in different stages of the testis.
Most researchers believed that the Y chromosome of cattle would be similar to the Y chromosome of other mammals, which does not have a large number of genes and is considered mostly transcriptionally inactive, Liu said. The Y chromosome, which was once similar to the X chromosome, evolved predominantly for testis development and male fertility, he added.
Currently, the gene content and transcription pattern of the bovine Y chromosome is the only non-primate Y chromosome that researchers have studied in depth, according to Liu.
"These findings directly contradict the traditional view that the Y is largely heterochromatic with a paucity of genes and transcription activity," said the researchers, who released their findings in the current online issue of Proceedings of the National Academy of Sciences.
The X and Y sex chromosome in most mammals began to diverge after 160 million years of evolution. However, genetic isolation and lineage-specific evolution resulted in the unique structure of the bovine Y chromosome, which determines the gene content and transcriptional activity of the Y chromosome among cattle, according to Liu.